We propose to continue our characterization of the anti-dextran idiotypes and anti-idiotypes. It is our long-term objective to use this system as a model for determining the role of idiotypes in immunoregulatory mechanisms and for developing strategies for artificially manipulating immune responese through idiotype-anti-idiotype recognition. There is a considerable literature supporting both concepts. Our starting point is a panel of hybridoma and myeloma derived dextran-binding proteins whose VH sequences and idiotype expression have been analyzed in detail. In addition, we have already described the fine specificity of a number of heterologous and monoclonal anti-idiotypic reagents. In the first part of this proposal, we will continue to produce heterologous and monoclonal anti-idiotypes for the purpose of characterizing the anti-dextran repertoire and developing reagents with which to artificially manipulate anti-dextran immune responses. Our approach will be to use both standard techniques for producing anti-idiotypes plus a new technique utilizing peptide mimicking VH region sequences as immunogens. We will develop reagents specific for V, D and possibly J segment sequences. In addition, reagents specific for the three hypervariable regions will also be produced. We will use these reagents to characterize the anti-dextran immune response in BALB/c as well as other strains of mice. We will then determine whether these reagents can be used to modulate immune responses and if so what mechanisms are involved. In the second part of this proposal we propose to use these existing and newly developed reagents to study the nature and function of syngeneic anti-idiotypic responses generated during anti-dextran responses. Using serological and plaque forming assays we will determine the isotype and fine specificity of these anti-ids. Are they specific for individual or cross-reactive idiotypes? In addition, we will measure the kinetics of anti-idiotype responses and determine their relationship to idiotype expression. Somatic cell hybridization techniques will be employed to capture syngeneic cells secreting anti-idiotypes so that the physical-chemical nature of these antibodies can be determined. Also we will pretreat animals with these well-characterized anti-idiotypes and determine their effect on anti-dextran immune responses.